Glycolysis Flashcards
definition of glycolysis
the breakdown of glucose to smaller molecules, so producing. the conversion of glucose to pyruvate
where does glycolysis take place
the cytoplasm of cells
what are the three chemical groups that come up in metabolism
aldehydes such as acetaldehyde (CH3CHO)
ketones such as acetone (CH3COCH3)
carboxyl groups such as acetic acid (CH3COOH)
what is the ending which denotes sugar
-ose
what is glucose also known as
hexose as it has six carbons (6 membered pyranose ring) , therefore one with three carbons would be known as triode and so on
what is important to remember about molecules
there is less space in molecules than would appear from the standard way they are represented
structure of fructose
froms a 5-membered (furanose) ring
what acids are common in metabolism
keto acids
Transamination
a chemical reaction that transfers an amino group to a ketoacid to form new amino acids
what makes up an amino acid
they have an amino group and an acid group and an R group, the amino group joins to the carboxyl group of its neighbour forming a peptide bond
Whats the first stage of glycolysis
phosphorylation:
this is the stage that consumes ATP
it traps glucose in the cell because glucose-6-P is ionised and unable to cross the cell membrane
What is the second stage of glycolysis
isomerization:
glucose-6-P is converted to fructose-6-P (these have the same molecular formula C6H12O6)
What is the third stage of glycolysis
another stage of phosphorylation:
again consuming ATP
it forms a hexose diphosphate that can be split into two phophorlytaed 3-carbon compounds
Fructose 1,6 - biphospahte
What is the fourth stage of glycolysis
cleavage + isomerization:
this forms two phosphorylated carbon compounds, then allows dihydroxyacetone-P to be converted to glyceraldehyde-3-P which can be metabolised
What is the 5th stage of glycolysis
oxidative phosphorylation:
gylceraldehyde-3-P is simultaneously oxidised and phosphorylated.
The hydrogen and electrons from glyceraldehyde-3-P are passed to nicotinamide adenine dinucleotide (NAD+)
In NAD what does R=
H
in NADP what does R=
Phosphate
Whats the role of vitamin B3 (niacin)
provides the nicotinamide part of the NAD+ molecule
needs to be provided in the diet
Lack of niacin causes what
pellagra - sensitivity to sunlight, dermatitis, alopecia, glossitis, weakness and ataxia (lack of muscle coordination)
What is the 6th stage in glycolysis
transfer of phosphate:
ATP PRODUCTION
2 molecules of ATP produced per molecule of glucose are consumed
What is the 7th stage
molecular rearrangement:
phosphate group moved from one position to another (isomerization)
What is the 8th stage
dehydration:
favours transfer of phosphate to ATP
What is the 9th stage
transfer of phosphate:
2 molecules of ATP Produced for every molecule of glucose consumed
Once this cycle is complete what happens under aerobic conditions
NAH+ is regenerated because NADH passes the electrons and the hydrogen atoms which recieves from glyceraldehyde-3-P though a system known as the electron transfer chain which combines therewith molecular oxygen to form water (also generates ATP)
Once this cycle is complete what happens under anerobic conditions (absence of molecular oxygen)
NADH builds up because NAD+ cannot be regenerated
if persisted glycolysis HALTS
How is NADH re-oxidised
by reducing pyruvate to lactate (this is responsible for muscle aches SPAGIE)
How does yeast get over the problem of anaerobic respiration
to regenerate NAH+ it converts pyruvate into ethanol
What are the three enzymes which regulate glycolysis
Hexokinase
Phosphofructokinase
Pyruvate kinase
Hexokinase
Catalyses: glucose → glucose-6-P)
Phosphofructokinase
Catalyses: fructose-6-P → fructose-1,6- bisphosphate
Pyruvate kinase
Catalyses: phosphoenolpyruvate → pyruvate
Major roles of phosphofructokinase
- High ATP allosterically inhibits the enzyme
- Low pH inhibits the enzyme (lactate accumulation)
- High citric aid inhibits
- High fructose-6-P stimulates the enzyme
